1. Field of the Invention
The present invention generally relates to a liquid crystal display device and a method of fabricating the same. More particularly, the present invention relates to a liquid crystal display device and a method for fabricating the same wherein column spacers may be provided outside an active region for maintaining a cell gap and for improving a cell gap yield.
2. Background of the Related Art
Over time, demands on display technology have gradually increased and resulted in the development of a wide variety of flat display panels including liquid crystal displays (LCDs), plasma display panels (PDPs), electro luminescent displays (ELDs), vacuum fluorescent displays (VFDs), etc. Some of the aforementioned flat panel display panels are currently used as displays of various apparatuses. Owing to their excellent picture display quality (e.g., resolution and brightness), light weight, thin dimensions, large screen manufacturable screen size, and low power consumption, LCDs are used as televisions (TVs), replacing conventional cathode ray tubes (CRTs), and are widely used in portable displays such as monitors of notebook computers and the like.
LCDs generally include a liquid crystal display panel for displaying a picture and driving circuits for providing driving signals to the liquid crystal display panel. The liquid crystal display panel generally includes first and second glass substrates bonded to each other and spaced apart from each other by a gap. A layer of liquid crystal material is injected into the gap between the first and second glass substrates.
The first glass substrate (i.e., the TFT array substrate) generally supports a plurality of gate lines arranged at a fixed interval and extending along a first direction, a plurality of data lines arranged at a fixed interval and extending along a second direction, perpendicular to the first direction, a plurality of pixel regions arranged in a matrix pattern and defined at crossings of the plurality of gate and data lines, pixel electrodes provided in respective ones of the pixel regions, and a plurality switching elements such as thin film transistors (TFTs) that are capable of transmitting a signal from the data line to the pixel electrodes in response to receiving a signal from the plurality of gate lines.
The second glass substrate (i.e., the color filter substrate) generally supports a black matrix layer for shielding light from portions of the liquid crystal display panel outside the pixel regions, and a color filter array having a red, green, blue (RGB) color filter layer for selectively transmitting light having predetermined wavelengths, and a common electrode for implementing a picture.
The first and second substrates are uniformly spaced apart from each other by spacers and are bonded together using sealant. The distance between the first and second substrates is called the cell gap. The sealant includes a liquid crystal injection hole through which liquid crystal material is injected.
Liquid crystal material is injected into the liquid crystal display panel by evacuating the cell gap and immersing the liquid crystal injection hole into liquid crystal material. Liquid crystal material then flows into the cell gap via a capillary phenomenon. After the liquid crystal material has been injected, the liquid crystal injection hole is sealed with sealant material.
The aforementioned liquid crystal injection method thus requires that two substrates be bonded together before liquid crystal material is injected into the cell gap. Disadvantageously, the aforementioned liquid crystal injection method requires a prohibitive amount of time to ensure that cell gaps of large LCDs are completely filled with liquid crystal material. To alleviate the aforementioned problem, a method has been suggested wherein the layer of liquid crystal material is formed by dispensing liquid crystal material directly onto a substrate prior to bonding the. first and second substrates together.
In fabricating LCDs via the aforementioned liquid crystal injection method, ball spacers must be evenly spread prior to bonding the substrates to ensure the cell gap between the two substrates is uniform. In fabricating LCDs via the aforementioned liquid crystal dispensing method, a patterned spacer or column spacer must be fixed to either the first or second substrate because ball spacers cannot effectively maintain a uniform cell gap when liquid crystal material is dispensed.
An LCD device and method for fabricating LCDs having column spacers will now be described in greater detail below. FIGS. 1A and 1B illustrate a layout of a related art LCD fabricated using column spacers. FIG. 1B illustrates a cross sectional view taken across a line I-I′ of FIG. 1A.
Referring to FIG. 1A, LCDs fabricated via the liquid crystal dispensing method are generally not fabricated one at a time. Rather, LCDs having different dimensions may be fabricated simultaneously. Accordingly, a plurality of LCDs (i.e., unit panels) are simultaneously fabricated out of bonded base substrates by separating unit panels from within the bonded substrates via scribing and breaking processes.
FIG. 1A illustrates two base substrates bonded together and including a plurality of unit panels having active regions A/A. Main sealant patterns 10 are formed on either of the two base substrates at a periphery of each active region to bond the two base substrates together and prevent liquid crystal material from leaking outside active regions A/A. Dummy sealant patterns 20 are formed within the dummy region outside the active regions A/A and maintain the uniformity of the cell gap between the two bonded base substrates in dummy regions outside the active regions A/A. Liquid crystal is dispensed directly onto either of the two bonded substrates.
Referring now to FIGS. 1A and 1B, EPD (End Point Detection) holes 9a for measuring and controlling an extent of etching and the dummy sealant patterns 20 are formed in the dummy region. When a portion of the dummy sealant pattern 20 is formed in the EPD hole 9a, the dummy sealant pattern 20 induces the cell gap to become non-uniform. More specifically, cell gaps of reflective or semi-transparent LCDs are approximately 2.5 μm. The depth of the EPD hole 9a is dependent upon the type of protection film used wherein protection films are usually formed of organic insulating material and have a thickness of about 2 μm. Further, in forming the EPD hole 9a, the gate insulating film is typically removed. In view of the above, EPD hole 9a usually have a depth close to the thickness of the cell gap. Therefore, portions of the dummy sealant patterns 20 that are formed within the EPD hole 9a create a non-uniform cell gap. Further, the presence of the dummy sealant patterns 20 in structures such as EPD holes 9a create gap spots 30 in active regions close to the EPD hole 9a. 
Related art solutions to the aforementioned problems of non-uniform cell gaps and gap spots generally include changing the positions. of structures such as EPD holes 9a and/or the dummy sealant patterns 20. These solutions, however, are difficult as they decrease the efficiency with which the surface area of the base substrates are used and they increase the difficulty of processing the unit panels once they are separated from the base substrates.